Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include<bits/stdc++.h>
#define rep(i,n)for(int i=0;i<(n);i++)
using namespace std;

int main() {
  int h,w;cin>>h>>w;
  int dy[4]={0,1,0,-1};
  int dx[4]={1,0,-1,0};
  vector<string> field(h);
  int count=0;
  rep(i,h) {
    cin>>field[i];
    rep(j,w) {
      if (field[i][j]=='.') count++;
    }
  }
  queue<pair<int,int>> q;
  vector<vector<int>> dist;
  dist.assign(h,vector<int>(w,-1));
  dist[0][0]=0;
  q.push(make_pair(0,0));
  while (!q.empty()) {
    int y=q.front().first;
    int x=q.front().second;q.pop();
    rep(i,4) {
      int ny=y+dy[i];
      int nx=x+dx[i];
      if (0 <= ny && ny < h && 0 <= nx && nx < w &&
                field[ny][nx] == '.' && dist[ny][nx] == -1) {
        q.push(make_pair(ny, nx));
        dist[ny][nx] = dist[y][x] + 1;
      }
    }
  }
  int best=dist[h-1][w-1];
  if (best==-1) {
    cout<<-1<<endl;
  }
  else cout<<count-best-1<<endl;
}